<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .item {
      display: block;
    }
    .submenu{
      display: none;
    }
    .item:hover .submenu{
      display: block;
    }
  </style>
</head>
<body>
  <div class="item">菜单1
    <ul class="submenu">
      <li>菜单项1</li>
      <li>菜单项2</li>
      <li>菜单项3</li>
      <li>菜单项4</li>
    </ul>
  </div>
  <div class="item">菜单2
    <ul class="submenu">
      <li>菜单项1</li>
      <li>菜单项2</li>
      <li>菜单项3</li>
      <li>菜单项4</li>
    </ul>
  </div>
  <div class="item">菜单3
    <ul class="submenu">
      <li>菜单项1</li>
      <li>菜单项2</li>
      <li>菜单项3</li>
      <li>菜单项4</li>
    </ul>
  </div>
  <div class="item">菜单4
    <ul class="submenu">
      <li>菜单项1</li>
      <li>菜单项2</li>
      <li>菜单项3</li>
      <li>菜单项4</li>
    </ul>
  </div>
</body>
</html>